fix: restart service after config change

When chrony was already installed, the service currently does not get
restarted when the config file is changed. I added a "watch" option to
the service.running state to ensure it gets a restart when we adapt the
configuration.

chrony/service/running.sls

     - enable: True
     - require:
       - sls: {{ sls_config_file }}
+    - watch:
+      - file: chrony-config-file-file-managed